1. Field of the Invention
The present invention relates generally to the field of biomass biorefining. More particularly, it concerns using metal compounds to enhance enzymatic hydrolysis of biomass material.
2. Description of Related Art
Lignocellulose biomass is considered a very desirable feedstock for biofuel production. Researchers have speculated that conversion of lignocellulose material could yield 25-50 billion gallons of ethanol per year if the fermentation process for lignocellulose can be optimized. As lignocellulose is a complex structural material made up of lignin, cellulose, and hemicellulose; a pretreatment step might be required to make the material amenable to cellulytic hydrolysis to convert the cellulose into fermentable sugars. Enzyme accessibility of the starting material is one of the key limiting steps for hydrolysis of lignocellulose in biorefining of biomass.
It has been recognized that lignin is one of the key, non-productive enzyme adsorption medium present in this material. Generally, lignin needs to be removed or at least reduced from the pretreated lignocellulosic substrate through an initial washing and separation step wherein cellulose is isolated for enzymatic saccharification and fermenting into biofuel. The initial washing steps typically involve use of copious amounts of water and include high temperatures leading to significant amounts of water and energy consumption, which not only increases costs, but also presents a serious environmental concern. Exogenous protein (bovine serum albumin-BSA) has been used to mask lignin to reduce adsorption of cellulase onto lignin enhancing enzymatic cellulose saccharification. Surfactants have also been used as lignin-block agents to improve enzymatic hydrolysis. Both of these techniques have hurdles that prohibit commercial applications. Proteins are too expensive to use in large scale production. Surfactants can cause foaming which may negatively impact saccharification and fermentation, and can also be expensive at its effective dosage.
Therefore, there exists a need for new methods to inhibit enzyme absorption by lignin during the biofuel production.